Answer:
Isostatic balance
Step-by-step explanation:
Just like an iceberg floats on water with parts of it submerged in water, the same is for the crust floating on the dense ‘liquid’ mantle. The heavier a part of the crust is, the more it is submerged into the mantle in the local region. Different regions of the lithosphere have different equilibriums depending on the local mass of the crust.